What must be true for the "are crossed by the outline of" selection method to function effectively?

For the "are crossed by the outline of" selection method to function effectively, it is essential that at least part of the edge from both features being considered is the same. This option reflects the fundamental principle of how geometrical intersections are determined in geographic information systems.

When you apply this selection method, the goal is to identify features that intersect with a designated boundary or outline. If the edges of the features do not overlap or share common segments, then they cannot be accurately assessed for intersection. Thus, having at least part of the edge shared ensures that the selection can reliably identify crossings and intersections between the defined boundary and the relevant features within the GIS dataset.

In contrast, the other choices suggest conditions that would either limit the capability of recognizing intersections or indicate that the features cannot interact geometrically. For effective use of intersection-based selection, it is crucial that there exists some degree of shared space or edge between the features involved.